Abstract: Described is an immortalized human skin cell type line (preferably keratinocytes, fibroblasts and/or endothelial cells) stably transfected with a vector, wherein said vector comprises a promoter inducible by environmental hazards and a reporter gene in operative linkage thereto. Preferably, the keratinocyte line is the line HaCaT, the fibroblast line is the line WI-26 and the endothelial cell line is the line LT-2. In addition, a living skin equivalent is described. Furthermore, in vitro toxicity assays making use of these immortalized human skin cell type lines or the skin equivalent are described.